The present invention is a system for remotely detecting the presence of an object. More particularly, one preferred embodiment of the invention supplies methods and apparatus for sensing concealed weapons to create a xe2x80x9cSafe Zone(trademark).xe2x80x9d The invention also includes novel signal processing methods and apparatus for providing high reliability object detection.
On Apr. 20, 1999, two students at the Columbine High School in Littleton, Colo. opened fire on their classmates and teachers with assault weapons. Twelve teenagers and one teacher were killed, and dozens of others were wounded. Tragic acts of violence like the Littleton massacre occur all too often in present day America. The Federal Bureau of Investigation reports that every year, criminals in the United States use firearms to commit over 2.4 million robberies, 5.6 million assaults, and 165,000 rapes. (See American Firearms Industry Journal, published by the National Association of Federally Licensed Firearms Dealers, www.amfire.com.) The Center for Disease Control has collected data showing that 247,979 xe2x80x9cfirearm deathsxe2x80x9d were recorded in the United States during the years 1986-1992. (Data compiled by the Center to Prevent Handgun Violence, www.handguncontrol.org.)
Many previous efforts to reduce the threat posed by the criminal use of firearms have met with limited success. In the past two decades, very expensive x-ray equipment has been installed in major airports. The machines are generally capable of detecting a metal gun in a very specialized, closed environment. This type of equipment requires a fixed installation, occupies a very large space, is close-range and may cost hundreds of thousands or even millions of dollars.
None of the complex concealed weapon detectors that are currently available in the commercial market are compact, lightweight, portable, easy to use, long-range and highly reliable. The development of such a device would constitute a revolutionary achievement and would satisfy a long felt need in the fields of law enforcement and security.
The present invention comprises methods and apparatus for detecting the presence of an object at a distance. One embodiment of the invention may be used to locate a concealed firearm carried by a person. The invention may be used to help keep weapons out of any secure area or xe2x80x9cSafe Zone(trademark),xe2x80x9d such as a school, bank, airport, embassy, prison, courtroom, office building, retail store or residence. The term xe2x80x9cSafe Zone(trademark)xe2x80x9d is a Trade and Service Mark owned by the Assignee of the present Patent Application, The MacAleese Companies, doing business as Safe Zone(trademark) Systems, Incorporated.
One embodiment of the invention utilizes low-power, horizontally polarized radio waves to illuminate a target, such as a person who may be entering a doorway. Radio waves reflected from the target are gathered by a receive antenna and then processed by a detector circuit. The presence of the concealed weapon is determined by solving an algorithm which utilizes measured differences in the amplitudes of waveforms that represent different polarized energy levels reflected back from the target, and which also utilizes stored values which represent the expected response of a person who is not carrying a weapon, as well as the response of a person carrying a weapon.
Novel signal processing techniques are then utilized to improve the reliability of the detection method. In one preferred embodiment of the invention, radiation reflected from the target is sensed and converted to a signal which is processed using Fast Fourier Transforms. In general, this method separates a first signal which is generated by radiation reflected from the target, that is generally well-behaved, from a second signal, which is generated by radiation reflected from a human body, that is generally chaotic.
One embodiment of the present invention offers the additional benefits of being compact, lightweight, long-range, portable and battery-operated. In another embodiment, the invention may be incorporated into automatic door-opening equipment. In yet another alternative embodiment, the invention may be used to locate inexpensive tags attached to merchandise as an inventory control and anti-shoplifting system.
An appreciation of other aims and objectives of the present invention and a more complete and comprehensive understanding of this invention may be achieved by referring to the drawings, and by studying the description of preferred and alternative embodiments.